A linear actuator as shown in FIG. 4 has been heretofore used in an electric part mounting apparatus, a semiconductor-related apparatus, or various industrial machines such as a machine tool and the like, and is suited to drive its linear motion mechanism. FIG. 4 shows a conventional moving magnet type linear actuator, in which FIG. 4(a) is a plan view thereof, FIG. 4(b) is a normal sectional view taken along a line of B-B in FIG. 4(a), and FIG. 4(a) corresponds to a perspective view, as seen in a direction of an arrow A in FIG. 4(b).
In FIG. 4, a reference numeral 1 is an armature, 2 is a stator base, 3 is a field permanent magnet, 4 is a field yoke, 6 is a linear guide rail, 7 is a sensor, 8 is a linear guide block, 9 is a linear scale part, 11 is a coil, 12 is a connection board, and 13 is a stopper.
In the linear actuator, the field yoke 4 is provided on the back of the field permanent magnet 3, and the field yoke 4 is used as both of a mover and a magnetic circuit. Further, the armature 1 has structure in which plural slotless coils 11 are provided on the connection board 12, and is arranged on the stator base 2 formed of a solid magnetic member through a magnetic gap for the mover, thereby to constitute the stator. On both sides of this armature 1, the linear guide rails 6 are fixed onto the stator base 2 in parallel, and the linear guide blocks 8 sliding on the linear guide rails 6 are fixed to lower portions of both end portions of the field yoke 4. Further, on a side surface of the mover, a magnet type linear scale 9 constituting a linear type encoder is arranged, and the sensor 7 for detecting the linear scale 9 is arranged on the stator base 2 so as to be opposed to this linear scale 9. Further, at end portions of the linear guide rail 6, stoppers 13 are provided in order to prevent the mover from overrunning.
This linear actuator has the magnetic circuit structure in which magnetic flux of the field permanent magnet 3 is interlinked with the stator base 2. Further, when the coil 11 of the armature is excited, the mover is moved linearly within a stroke of a difference between the armature length and the mover length by a moving magnetic field formed by the field magnet and the armature (refer to, for example, Patent Document 1).
Patent Document 1:
JP-A-9-266659 (page 5 in specification, FIG. 3)